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We now carry out servicing to your vehicles air
condtioning:
A recharge and filter of your exsisting air conditioning
system will improve its effectivness and prolong the life of the components
within the sytem, air con systems should be used every day even in the winter
to ensure that the lubircants within are circulated and stop seals drying
out
Vehicles are found to have primarily three
different types of air conditioning systems. While each of the three types
differ, the concept and design are very similar to one another. The most common
components which make up these automotive systems are the following:
Note: if your car has an Orifice tube, it will
not have a Thermal Expansion Valve as these two devices serve the same purpose.
Also, you will either have a Receiver-Dryer or an Accumulator, but not both.
COMPRESSOR
Commonly referred to as the heart of the system,
the compressor is a belt driven pump that is fastened to the engine. It is
responsible for compressing and transferring refrigerant gas.
The A/C system is split into two sides, a high
pressure side and a low pressure side; defined as discharge and suction. Since
the compressor is basically a pump, it must have an intake side and a discharge
side. The intake, or suction side, draws in refrigerant gas from the outlet of
the evaporator. In some cases it does this via the accumulator.
Once the refrigerant is drawn into the suction
side, it is compressed and sent to the condenser, where it can then transfer the
heat that is absorbed from the inside of the vehicle.
CONDENSER
This is the area in which heat dissipation
occurs. The condenser, in many cases, will have much the same appearance as the
radiator in you car as the two have very similar functions. The condenser is
designed to radiate heat. Its location is usually in front of the radiator, but
in some cases, due to aerodynamic improvements to the body of a vehicle, its
location may differ. Condensers must have good air flow anytime the system is in
operation. On rear wheel drive vehicles, this is usually accomplished by taking
advantage of your existing engine's cooling fan. On front wheel drive vehicles,
condenser air flow is supplemented with one or more electric cooling fan(s).
As hot compressed gasses are introduced into the
top of the condenser, they are cooled off. As the gas cools, it condenses and
exits the bottom of the condenser as a high pressure liquid.
Located inside the vehicle, the evaporator serves
as the heat absorption component. The evaporator provides several functions. Its
primary duty is to remove heat from the inside of your vehicle. A secondary
benefit is dehumidification. As warmer air travels through the aluminum fins of
the cooler evaporator coil, the moisture contained in the air condenses on its
surface. Dust and pollen passing through stick to its wet surfaces and drain off
to the outside. On humid days you may have seen this as water dripping from the
bottom of your vehicle. Rest assured this is perfectly normal.
The ideal temperature of the evaporator is 32¦
Fahrenheit or 0¦ Celsius. Refrigerant enters the bottom of the evaporator as a
low pressure liquid. The warm air passing through the evaporator fins causes the
refrigerant to boil (refrigerants have very low boiling points). As the
refrigerant begins to boil, it can absorb large amounts of heat. This heat is
then carried off with the refrigerant to the outside of the vehicle. Several
other components work in conjunction with the evaporator. As mentioned above,
the ideal temperature for an evaporator coil is 32¦ F. Temperature and pressure
regulating devices must be used to control its temperature. While there are many
variations of devices used, their main functions are the same; keeping pressure
in the evaporator low and keeping the evaporator from freezing; A frozen
evaporator coil will not absorb as much heat.
PRESSURE REGULATING DEVICES
Controlling the evaporator temperature can be
accomplished by controlling refrigerant pressure and flow into the evaporator.
Many variations of pressure regulators have been introduced since the 1940's.
Listed below, are the most commonly found.
ORIFICE TUBE
The orifice tube, probably the most commonly
used, can be found in most GM and Ford models. It is located in the inlet tube
of the evaporator, or in the liquid line, somewhere between the outlet of the
condenser and the inlet of the evaporator. This point can be found in a properly
functioning system by locating the area between the outlet of the condenser and
the inlet of the evaporator that suddenly makes the change from hot to cold. You
should then see small dimples placed in the line that keep the orifice tube from
moving. Most of the orifice tubes in use today measure approximately three
inches in length and consist of a small brass tube, surrounded by plastic, and
covered with a filter screen at each end. It is not uncommon for these tubes to
become clogged with small debris. While inexpensive, usually between three to
five dollars, the labor to replace one involves recovering the refrigerant,
opening the system up, replacing the orifice tube, evacuating and then
recharging. With this in mind, it might make sense to install a larger pre
filter in front of the orifice tube to minimize the risk of of this problem
reoccurring. Some Ford models have a permanently affixed orifice tube in the
liquid line. These can be cut out and replaced with a combination filter/orifice
assembly.
THERMAL EXPANSION VALVE
Another common refrigerant regulator is the
thermal expansion valve, or TXV. Commonly used on import and aftermarket
systems. This type of valve can sense both temperature and pressure, and is very
efficient at regulating refrigerant flow to the evaporator. Several variations
of this valve are commonly found. Another example of a thermal expansion valve
is Chrysler's "H block" type. This type of valve is usually located at the
firewall, between the evaporator inlet and outlet tubes and the liquid and
suction lines. These types of valves, although efficient, have some
disadvantages over orifice tube systems. Like orifice tubes these valves can
become clogged with debris, but also have small moving parts that may stick and
malfunction due to corrosion.
RECEIVER-DRIER
The receiver-drier is used on the high side of
systems that use a thermal expansion valve. This type of metering valve requires
liquid refrigerant. To ensure that the valve gets liquid refrigerant, a receiver
is used. The primary function of the receiver-drier is to separate gas and
liquid. The secondary purpose is to remove moisture and filter out dirt. The
receiver-drier usually has a sight glass in the top. This sight glass is often
used to charge the system. Under normal operating conditions, vapor bubbles
should not be visible in the sight glass. The use of the sight glass to charge
the system is not recommended in R-134a systems as cloudiness and oil that has
separated from the refrigerant can be mistaken for bubbles. This type of mistake
can lead to a dangerous overcharged condition. There are variations of
receiver-driers and several different desiccant materials are in use. Some of
the moisture removing desiccants found within are not compatible with R-134a.
The desiccant type is usually identified on a sticker that is affixed to the
receiver-drier. Newer receiver-driers use desiccant type XH-7 and are compatible
with both R-12 and R-134a refrigerants.
ACCUMULATOR
Accumulators are used on systems that accommodate
an orifice tube to meter refrigerants into the evaporator. It is connected
directly to the evaporator outlet and stores excess liquid refrigerant.
Introduction of liquid refrigerant into a compressor can do serious damage.
Compressors are designed to compress gas not liquid. The chief role of the
accumulator is to isolate the compressor from any damaging liquid refrigerant.
Accumulators, like receiver-driers, also remove debris and moisture from a
system. It is a good idea to replace the accumulator each time the system is
opened up for major repair and anytime moisture and/or debris is of concern.
Moisture is enemy number one for your A/C system. Moisture in a system mixes
with refrigerant and forms a corrosive acid. When in doubt, it may be to your
advantage to change the Accumulator or receiver in your system. While this may
be a temporary discomfort for your wallet, it is of long term benefit to your
air conditioning system. |
